John Joseph Frederick Otto Zardetti ( January 24, 1847 – May 10, 1902) was a Swiss prelate of the Roman Catholic Church. He served as archbishop of the Archdiocese of Bucharest in what is today Romania from 1894 to 1895. Zardetti previously served as the first bishop of the new Diocese of Saint Cloud in Minnesota in the United States from 1889 to 1894. After resigning as archbishop, Zardetti briefly served in the Roman Curia with the title of titular archbishop of Mocissus.